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Diffstat (limited to 'man2/sched_rr_get_interval.2')
| -rw-r--r-- | man2/sched_rr_get_interval.2 | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/man2/sched_rr_get_interval.2 b/man2/sched_rr_get_interval.2 new file mode 100644 index 0000000..cbd6247 --- /dev/null +++ b/man2/sched_rr_get_interval.2 @@ -0,0 +1,110 @@ +.\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996 +.\" +.\" SPDX-License-Identifier: GPL-2.0-or-later +.\" +.\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se> +.\" First version written +.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de> +.\" revision +.\" +.TH sched_rr_get_interval 2 2023-03-30 "Linux man-pages 6.05.01" +.SH NAME +sched_rr_get_interval \- get the SCHED_RR interval for the named process +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <sched.h> +.PP +.BI "int sched_rr_get_interval(pid_t " pid ", struct timespec *" tp ); +.fi +.SH DESCRIPTION +.BR sched_rr_get_interval () +writes into the +.BR timespec (3) +structure pointed to by +.I tp +the round-robin time quantum for the process identified by +.IR pid . +The specified process should be running under the +.B SCHED_RR +scheduling policy. +.PP +If +.I pid +is zero, the time quantum for the calling process is written into +.IR *tp . +.\" FIXME . On Linux, sched_rr_get_interval() +.\" returns the timeslice for SCHED_OTHER processes -- this timeslice +.\" is influenced by the nice value. +.\" For SCHED_FIFO processes, this always returns 0. +.\" +.\" The round-robin time quantum value is not alterable under Linux +.\" 1.3.81. +.\" +.SH RETURN VALUE +On success, +.BR sched_rr_get_interval () +returns 0. +On error, \-1 is returned, and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EFAULT +Problem with copying information to user space. +.TP +.B EINVAL +Invalid pid. +.TP +.B ENOSYS +The system call is not yet implemented (only on rather old kernels). +.TP +.B ESRCH +Could not find a process with the ID +.IR pid . +.SH VERSIONS +.SS Linux +Linux 3.9 added +.\" commit ce0dbbbb30aee6a835511d5be446462388ba9eee +a new mechanism for adjusting (and viewing) the +.B SCHED_RR +quantum: the +.I /proc/sys/kernel/sched_rr_timeslice_ms +file exposes the quantum as a millisecond value, whose default is 100. +Writing 0 to this file resets the quantum to the default value. +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +POSIX.1-2001. +.SS Linux +POSIX does not specify any mechanism for controlling the size of the +round-robin time quantum. +Older Linux kernels provide a (nonportable) method of doing this. +The quantum can be controlled by adjusting the process's nice value (see +.BR setpriority (2)). +Assigning a negative (i.e., high) nice value results in a longer quantum; +assigning a positive (i.e., low) nice value results in a shorter quantum. +The default quantum is 0.1 seconds; +the degree to which changing the nice value affects the +quantum has varied somewhat across kernel versions. +This method of adjusting the quantum was removed +.\" commit a4ec24b48ddef1e93f7578be53270f0b95ad666c +starting with Linux 2.6.24. +.SH NOTES +POSIX systems on which +.BR sched_rr_get_interval () +is available define +.B _POSIX_PRIORITY_SCHEDULING +in +.IR <unistd.h> . +.\" .SH BUGS +.\" As of Linux 1.3.81 +.\" .BR sched_rr_get_interval () +.\" returns with error +.\" ENOSYS, because SCHED_RR has not yet been fully implemented and tested +.\" properly. +.SH SEE ALSO +.BR timespec (3), +.BR sched (7) |